Device designed to detect toxic gases and chemical warfare agents

Schematic of the prototype.

Troy, N.Y. — Researchers at Rensselaer Polytechnic Institute have been awarded a $1.3 million Nanoscale Interdisciplinary Research Team (NIRT) grant from the National Science Foundation (NSF) to further develop nanoscale chemical sensors using carbon nanotubes designed to detect toxic gases and chemical warfare agents.

“Traditionally, it could take several days to get gas analysis results back from a lab, but first responders don’t have that kind of time. They need answers immediately,” said Nikhil Koratkar, assistant professor of mechanical, aerospace, and nuclear engineering at Rensselaer and principal investigator on the project. “We are working to develop a system that alerts them to dangers in real time at the site of an emergency using a device that is battery-powered and transportable, such as a coin-sized device worn on a uniform or on a vehicle.”

In 2003, the team developed a prototype sensor that demonstrated definitive identification of contaminants in real time. This new NSF grant will support research to boost the sensitivity of the device from identifying gases at concentrations of parts per hundred, as in the prototype, to parts per million, according to Koratkar. To do this, his team will examine how the size, shape, and density of the nanotubes and the overall geometry of the device affects the sensitivity levels.

In the prototype, billions of carbon nanotubes sit in a silicon substrate. The sharp tips of the tubes greatly amplify the surrounding electric field, inducing ionization and electrical breakdown of gases at low voltages. All gases are classified by their different breakdown voltages—essentially a dictionary of gas fingerprints. Once the voltage fingerprint is known, the gas can be identified. By monitoring the discharge current, it is possible to determine the gas concentration, said Koratkar. The team’s research was published in Nature (Vol. 424, 171, 2003).

For maximum effectiveness, the nanotube tips must be vertically aligned when they are exposed to gas molecules. Controlling the growth of nanotubes is a technique pioneered by Pulickel Ajayan, Rensselaer professor of materials science and engineering, and member of the research team developing the sensors. Other team members include Theodorian Borca-Tasciuc, assistant professor of mechanical, aerospace, and nuclear engineering; Steven Cramer, professor of chemical engineering; and Saroj Nayak, assistant professor of physics.

The prototype is a breakthrough from traditional electrical-conductivity-based gas detectors, in which molecules must adsorb, or cling, to a thin film surface, thereby changing the film’s electrical properties. However, such sensors display slow response times and are not suitable for definitive identification, according to Koratkar.

A $50,000 grant in 2002 from Rensselaer’s Seed Funding Program jumpstarted the team’s research. The program is designed to support innovative and interdisciplinary projects that have a high probability of attracting major external funding.

Koratkar joined the Rensselaer faculty in 2001. He is a collaborator on nanotechnology research associated with Rensselaer’s Center for Directed Assembly of Nanostructures, one of only six NSF Nanoscale Science and Engineering Centers in the United States.

Contact: Mary Cimo
Phone: (518) 687-7174
E-mail: cimom@rpi.edu